This project involves the computer-based mathematical analysis, pattern recognition, and image processing in support of diagnostic activities in the Diagnostic Imaging, Department of the Clinical Center and collaborating Institutes. Applications include computerized ECG-gated radionuclide angiocardiography, scintigraphic studies of regional cerebral blood flow, scintigraphic studies of gastric fluid dynamics, pulmonary ventilation-perfusion scintigraphs, and computer analysis of ultrasonograms. BIBLIOGRAPHIC REFERENCES: Agress, H. Jr., Bacharach, S.L., Hammock, M.K., Green, M.V., Johnston, G.S., Di Chiro, G.: Stochastic analysis of 133-Xe clearance for determining regional cerebral blood flow in a primate model. Stroke 8: 222-226, March 1977. Line, B.R., Jones, A.E., Johnston, G.S., Crystal, R.G., Bailey, J.J.: An algorithm for the selection of lung margins in scintigraphic ventilation-perfusion studies. Proceedings of the Sixth Symposium for the Sharing of Computer Programs and Technology in Nuclear Medicine. Society for Nuclear Medicine, 475 Park Avenue South, New York, N.Y., 10016, 1976, pages 52-59.